Exercise-Heat Tolerance of College Distance Runners at 38 °C

This investigation evaluated the relative exercise-heat tolerance (EHT) of highly trained athletes. Eleven anthropometric and personal characteristics of 12 male distance runners were measured. The runners underwent two strenuous exercise tests: treadmill running at 240 and 270 m · min^-1, 20 min total, one in a mild (23 °C) and one in a hot (38 °C) environment. The heart rate (HR), plasma lactate (LA), and plasma glucose differences between the 23 and 38 °C tests were used to describe each runner's relative EHT. Multiple linear regression analysis indicated that no personal characteristics were valid predictors of EHT. Physiological responses during the 38 °C test demonstrated that HR, LA, and plasma glucose were affected by between-subject differences in relative exercise intensity but rectal temperature and change in plasma volume were not. These findings suggest that EHT in a hot environment may be predicted by evaluating HR, LA, and glucose responses, to allow identification of distance runners who may have low or high EHT.